1. Field of the Invention
The present invention relates to an aluminum nitride sintered body suitable for use in a member for a semiconductor-manufacturing device such as a substrate material for an electrostatic chuck, and a method of manufacturing the same.
2. Description of the Related Art
Since aluminum nitride (AlN) exhibits high corrosion resistance to a halogen gas, it has been widely used as a material for a substrate of an electrostatic chuck. In the electrostatic chuck using a Johnson-Rahbek force, a material for the substrate desirably has a volume resistivity of about 108 to 1012 Ω·cm in order to attain a high adsorption force and a high responsiveness of the electrostatic chuck. However, in general, the volume resistivity of aluminum nitride decreases to 107 Ω·cm or less at high temperature of 300° C. or more. Therefore, aluminum nitride cannot be used as a material for the substrate of an electrostatic chuck at high temperatures. In view of these circumstances, as disclosed in Japanese Patent Application Laid-open Nos. H9-315867 and 2003-55052, attempts have been made to improve the volume resistivity of aluminum nitride at high temperatures.
However, because the volume resistivity of conventional aluminum nitride has a high dependency upon temperature, when the conventional aluminum nitride is used as a substrate material for an electrostatic chuck, the workable temperature range for the electrostatic chuck is limited.
The present invention has been achieved in order to solve the above problem, and an object of the invention is to provide an aluminum nitride sintered body that exhibits suitable volume resistivity when it is used in a substrate material for an electrostatic chuck at high temperatures, and low in temperature dependency of the volume resistivity, and a method of manufacturing the aluminum nitride sintered body.